Generally, hip stem implants come in a variety of common shapes and sizes to accommodate the vast majority of patients requiring a hip stem replacement. To ensure a proper seating of the hip stem a like variety of shaped and sized rasps are provided to properly form the proximal medullary canal of the femur. Therefore, for each size and shape of prosthetic hip stem implant there is generally a correspondingly sized and shaped rasp. Typically a hospital would have on hand a complete set of commonly sized and shaped rasps. After one of the common rasps is used, it is cleaned and sterilized for use over and over again.
A problem is experienced when, for reasons not detailed here, a prosthetic hip stem implant is required which is of an uncommon shape or size. In such circumstances, the manufacturer is called upon to create a "one of a kind" implant for the patient. This may be accomplished in a number of valid methods but perhaps is more commonly accomplished through computer aided design and computer numerical controlled milling machines. This known process is able to accurately and economically produce the off sized or irregularly shaped implant as required. As mentioned, it is common for a corresponding rasp to be provided for a particular size of implant. Therefore, the rasp provided for the one of kind implant is itself "one-of-a-kind" in size and shape.
Heretofore, the one-of-a-kind rasps for the one-of-a-kind implant are formed from the same material as the reusable more commonly sized rasps. To manufacture the one-of-a-kind rasp a significant amount of skilled labor is required to machine and cut the rasp teeth in its outer surface. Such a process is labor intensive and thereby costly to a manufacturer. While it is true the rasp may be formed on a CNC machine consistent with the industry practice regarding common size rasps, such is considered expensive and equally labor intensive in terms of re-tooling time, down time for re-tooling, lost machine productivity and engineering time. Therefore, the hand grinding approach to producing the one-of-a-kind rasp is considered to be the least burdensome of the two methods. The cost of the special rasp is especially burdensome when it is considered that the rasp is not for reuse and should be discarded after surgery since it is unlikely that the exact one-of-a-kind implant corresponding to the rasp would ever be called for again.
Therefore, for each special implant sold by a manufacturer a special rasp is required which is discarded after use. Finally, manufacturing the rasp in the manner described above is a time consuming process and requires additional lead time before delivery to the surgeon.